YA about two girls that disproved a house with a mysterious chair in it.

[Jamile]

So there’s this girl that recently moved to a rather rural town that’s on the edge of a cliff area in the UK (i think) with her father and she starts of by befriending the other girl in the village. And together the go off to explore this abandoned house just outside of town. And there’s this chair in one of the rooms with cuffs on it. And so the two girl continue on with their days, becoming friend over the next period of time
And that the same time of all this there’s another person who’s writing some of the chapters (around a couple hundred years before the present day of the book is set).
And the chair is a really important plot point, they return back to the house several times to discover that the chair is attached to a railway sort of system that sends the occupent of it to their deaths (by decapitation). And at the end of the book the girl who was originally in the village dies because she falls off a cliff.
I read this back in 2016/17, but I’m fairly certain that it was published in the 2000s. I could be wrong though.

[Daisy]

Jamile, what do you mean when you say the girls disproved the house?